jim8flog
Journeyman Pro
Well, on a par and course rating 72 with slope 142, an average differential of 11.3 gives an exact handicap of 9. That is an average (of 8) score of 83.3 so the range could well include a 87.
Having slept on it. I would add that one of the major points is of the WHS is that if you put in enough cards on a regular basis it your Handicap Index should reflect current ability more quickly than the UHS (with the UHS it takes ten bad rounds to get a one shot increase) and without a handicap review you might never be at the handicap level to suit ability.
Now if the 75 you had was a one off, scored say a year ago and was an exceptional score or thereabouts it is natural for it to fall off and bring you back to a handicap index to suit your current ability.
I now remember back in March doing an illustrative record for a similarly handicapped player who was declining in ability and with a space of 3 records being added to their record they saw a 1.5 increase in their handicap index.